Typically, the above referenced forming, filling and sealing machines are adapted to receive flat blanks, open same into a tube, form and seal one end of the tube, fill the container with the desired liquid, and form and seal the other end.
The thus formed bottom end of the container, while generally flat, tends to bulge downwardly once the container is filled due to the flexibility of the paperboard and, hence, may not stand directly upright during storage and shipping.
Kume et al U.S. Pat. No. 4,838,847 discloses a container which is recessed in the central portion of its bottom so as to seat stably. The recessed bottom is formed first on a mandrel whose end surface defines a pyramidal-shaped cavity for cooperation with a projection complementary to the cavity formed on the face of a press member serving to form the recess on the container bottom therebetween when sealed under pressure.